what does the # sign mean in xml

Question

I am pretty new to xml and spring and am trying to follow an xml file and I found these lines:

<bean id="urlResource" class="org.springframework.core.io.UrlResource">
    <constructor-arg index="0" type="java.net.URL" value="classpath:config/config-#{environment}.properties" />
</bean>

I am not sure if the # is a feature of xml or a feature of spring. Does anyone have an explanation?

Answer 1

It's a Spring feature. #{...} is an SpEL expression.